Ok, but the orange taraccota ones are ok right? Anything not glazed or painted? Also what is your opinion on heater placement? I have my 50w Aqueon vertically next to the filter. I also read people say to put it on a 45 degree angle.
I've used teracotta pots in my 5.5, they are great. ALgae will grow on them, but IMO it looks really cool, though that is a more natural tank (if you ignore the castle and Captain America...)
My filter placement depends on my hood and decor...some hoods have only specific places a filter CAN go. All mine are vertical, the thermometer across the tank to get the best reading n overall heat. Since yours is next to the filter, the warm water will be circulated more. I really think it's a matter of preference...I prefer my heaters vertical for looks, to be honest xP My bettas have never minded